In one of the most visceral images of corruption within the body, the ghost of Hamlet’s father describes his murder by poison at the hands of Claudius:
Upon my secure hour thy uncle stole,
With juice of cursed hebenon in a vial,
And in the porches of my ears did pour
The leperous distilment; whose effect
Holds such an enmity with blood of man
That swift as quicksilver it courses through
The natural gates and alleys of the body,
And with a sudden vigour doth posset
And curd, like eager droppings into milk,
The thin and wholesome blood: so did it mine. [emphasis mine] (1.3.61-70)
The power of the image comes from comparing the curdling effects of poison on the blood to the daily and material reality of milk going bad. As we and our early modern counterparts were familiar, the process of milk putrefying involved the separation of the solids and the liquids of the milk, as Shakespeare so eloquently put it, “like eager droppings into milk.” If the thickening of blood could be described in terms of the curdling of milk, I wondered: could the danger of curdled blood be applied quite literally to breast milk, which was thought to be a form of blood?
My investigation of this as a potential phenomenon began by considering Old Hamlet’s speech alongside the transformation Lady Macbeth calls for, to “make thick my blood…Come to my woman’s breasts, / And take my milk for gall” (1.5.43, 47-8). Her references to her milk have been explored as one of Shakespeare’s many references to breastfeeding, and central to discussions of early modern breastfeeding was the status of human breast milk. Since antiquity, as Laurence Totelin has written, breast milk was held to be an especially nutritive substance with healing qualities. It was a powerful substance capable of changing or altering the children who ingested it because it was thought to be “white blood” or “‘twice-concocted’ blood manufactured in the mammary glands from blood itself.” But as I am interested in the darker underbelly of milk as an easily corruptible substance, I wanted to find out more about milk curdling and to what extent it was a physiological as much as a culinary phenomenon.
There were a variety of early modern remedies directed towards breastfeeding women, treating everything from “for a milk sore in the breast,” to “A Medecine to to drye vpp a woemans Milke troubling her in Childbedd,” to remedies “To Increase A Womans Milk” or “For a woman that hath lost her milke.” Among these, sure enough, I found remedies that specifically mentioned the curdling of milk in the breast, providing some clues about the physical pain and hardness associated with the problem. Lady Frances Catchmay provided a remedy “for a Womans brest that is curdeled | wth milke” in her manuscript receipt book. So too, Philip Stanhope recorded two receipts, one from “L[ady]. Hu.” for a remedy “Against the sorenesse of any breasts by reason of the Curdling of milke in womens Breasts,” and another for “A Cattaplasme for Breasts that are hardned with congealed milke.”
Lady Ayscough’s receipt book provided a remedy for “Brest curdled with Milk to help,” but also one “For a Breast wherein | the Milk is wharled & knotted”–what an image!–which required a massage to “breake the wharles | easily with your finger morneing and euening.”
Clearly, curdled milk in the breasts was a common problem, and a painful one at that, even, as one recipe notes, causing “rednes inflamation | swelling paine and torment.” In light of evidence that milk could in fact curdle in the breasts, Lady Macbeth’s desire to “make thick my blood…And take my milk for gall” (1.5.43, 48) can be read as need for physiological hardening to accompany her emotional stoicism. Regardless of whether we think that Lady Macbeth’s spirits could enact such a transformation upon her body, or if she means it purely for the sake of metaphor, her desire for such a painful state is in stark contrast to the solace that most women were seeking for their breast pain. For such a well-documented problem among early modern women, how much more unnatural that Lady Macbeth should wish it! Perhaps we can’t help but admire her intention to practice what she preaches to her husband: no pain, no gain.
 Ken Albala, “Milk: Nutritious and Dangerous,” in Milk: Beyond the Dairy: Proceedings of the Oxford Symposium on Food and Cookery, 1999, (Devon, UK: Prospect Books, 2000), 21. See also Victoria Sparey’s discussion of blood and milk in “Identity-Formation and the Breastfeeding Mother in Renaissance Generative Discourses and Shakespeare’s Coriolanus,” Social History of Medicine 25.4 (2012), pp. 781-87.
 Anne Brumwich (and others), Wellcome MS 160, f. 89v, c. 1625-1700; Mrs. Corlyon, Wellcome MS 213, f. 38v, 1606; Elizabeth Jacob (and others), Wellcome MS 3009, f. 78r, 1654-c. 1685; Jane Jackson, Wellcome MS 373, f. 111r, 1642.
 Lady Frances Catchmay, Wellcome MS 184A, f. 35v, c. 1625.
 Philip Stanhope, Wellcome MS 761, ff. 182v, 197v, c. 1635.
 Lady Ayscough, Wellcome MS 1026, ff. 112v, 83r, 1692.
 Townshend Family, Wellcome MS 774, f. 21v, 1636-1647.